My dad doesn't use the Veterans Assistance clinic, does that mean he cannot get long term care benefits?

I don't believe he'd be limited to VA doctors only. Depending on where he lives, the VA may or may not have the right doctors to treat him. If they don't they'd have him see another doctor. None of that should affect his VA benefits, however. Please contact your local Veteran's advocate or call the VA for information. I hope he gets the best care possible.
Carol